This application is based on Japanese Patent Application No. 2000-26219 filed on Feb. 3, 2000 the contents of which are incorporated herein by reference.
1. Field of Invention
The present invention relates to a stator of a rotary electric machine mounted on a passenger vehicle, truck or the like. Specifically, the present invention prefers to a stator of an alternator for vehicle.
2. Description of Related Art
Engine room capacity of vehicles in recent years has become smaller as the vehicle has changed to a slanted nose configuration to reduce traveling resistance and to maintain space for passengers. Therefore, the environmental temperature of an alternator has increased. Further, increasing an output of the alternator is required in compliance with increasing of various electric loads, such as a safety control device. As a result, heat generated by the alternator has been increasing. Further, erosion and electric short circuiting are facilitated, when a tire splashes the alternator with water, or when the alternator has water poured on it when the engine room is washed and the like. In cold regions water may contain an anti-freezing agent that is an electrolytic solution. Of course, there is also a requirement to cut costs while maintaining temperature reduction and durability against an environment.
In consideration of the above-mentioned circumstances, the applicant filed JP-B-2927288 and U.S. Pat. No. 5,998,903 that disclose an alternator that has a winding using a plurality of hairpin shaped segments made of an electric conductor. This winding is assembled by inserting the segments into slots of a stator core and joining the segments. In this arrangement, it is possible to reduce resistance of the winding by increasing a space factor of the winding in the slots and to achieve a decrease in temperature and an increase in output. Further, the alternator has insulators having a S-shaped radial cross-section. The S-shaped insulator is disposed between the segments in the slot and between the segments and the slot to eliminate an insulating layer on the segment surface. Therefore, the segments decrease costs.
However, it is difficult to insert the segments wrapped in the S-shaped insulators into the slot. Therefore, the assembling process is complicated. On the other hand, to increase the space factor is not as easy as expected, because it is necessary to prevent the undesirable movement of the insulator between the segments when the segments are inserted after inserting the insulators into the slot.
The present invention addresses these drawbacks by providing an improved stator arrangement.
It is therefore an object of this invention to provide an improved stator of a rotary electric machine for a vehicle.
It is a further object of this invention to provide a stator of a rotary electric machine for a vehicle which is capable of improving the assembly process.
It is another object of this invention to provide a stator of a rotary electric machine for a vehicle which is capable of improving a space factor.
It is a still further object of this invention to provide a stator of a rotary electric machine for a vehicle which is capable of improving durability against the environment.
According to a first aspect of the present invention, the stator of the rotary electric machine for a vehicle comprises a stator core having a plurality of slots, a poly-phase stator winding disposed in the slots and an insulator insulating between the slots and the stator winding. The stator winding comprises a plurality of segments having covered segments, each covered with an insulating layer, and bare segments have no insulating layer. The bare segments are adjacent to only the covered segments in the slots.
Although the bare segment is disposed in the slot, it is possible to insulate the segments in the slots from each other.
The segments may be formed in at least a substantial U-shape. The segments extend from both axial sides of the stator core to form first and second coil ends groups. The first coil ends have turn portions of the U-shaped segments. The second coil ends have a plurality of joining portions joining a pair of ends of the different U-shaped segments extending from the slots spaced apart at a predetermined pitch each other.
The turn portions may have small turn portions surrounding no other turn portions, which are provided by the covered segments. The segment having the small turn portion has a pair of straight portions disposed in the slots that are adjacent to the other straight portions belonging to the other segment having the small turn portion. It is possible to insulate the segments having the small turn portions even if the bare segments are used in the stator winding.
The turn portions may comprise first turn portions which is the smallest, second turn portions surrounding the first turn portions, third turn portions surrounding the second turn portions and forth turn portions surrounding the third turn portions. The covered segments provide the first and third turn portions. The bare segments provide the second and forth turn portions. In this arrangement, the bare segments are not adjacent to each other in both of the slots and the coil ends groups.
The turn portions may have small turn portions provided by the covered segments and large turn portions provided by the bare segments surrounding the small turn portions.
The turn portions may have a pair of the small turn portions provided by the covered segments being arranged side by side in a radial direction of the stator core and the large turn portions provided by the bare segments surrounding them.